1. Field of the Invention
The present invention relates to a process for producing pentacyl-type crystalline zeolites and a process for producing .epsilon.-caprolactam by use of the same.
2. Description of the Related Art
.epsilon.-Caprolactam is an important and fundamental chemical material used as a starting material for producing nylon etc., and one of proposed processes for producing .epsilon.-caprolactam is Beckmann rearrangement (gaseous-phase Beckmann rearrangement) of cyclohexanone oxime under gaseous-phase reaction conditions in the presence of a pentacyl-type crystalline zeolite catalyst (e.g., JP-A 2-275850 and JP-A 2-250866).
Pentacyl-type crystalline zeolites are produced by hydrothermal synthesis reaction of a silicon compound such as tetraalkyl orthosilicate by using a compound such as tetrapropyl ammonium hydroxide as the so-called template agent. Such a process has problems such that a pentacyl-type crystalline zeolite having high activity cannot always be obtained. Further, in such a process, the unreacted silicon compound and the unreacted tetrapropyl ammonium hydroxide remain in the residual solution obtained after the product zeolites were recovered, and thus their recycling for use is considered appropriate, but there is a problem in that even if such unreacted materials are recycled and used as the starting materials in the hydrothermal synthetic reaction, a pentacyl-type zeolite having high catalytic activity is hardly obtained with good reproducibility.